In underground drilling applications, such as oil and gas or geothermal drilling, a borehole is drilled through a formation deep in the earth using a downhole drilling rig. Such boreholes are drilled or formed by a drill bit connected to a drill string of the rig.
The downhole drilling rig often includes measurement tools for gathering information regarding the formation as it is being drilled through, using techniques commonly referred to as Measurement-While-Drilling (MWD) or Logging-While-Drilling (LWD). Electronic components that operate under downhole drilling conditions, such as printed circuit board assemblies (PCBAs) in the measurement tools can be exposed to the high temperature, which often exceeds the maximum temperature rating of the normal electronic components. For example, the temperature of the formation surrounding deep wells, especially geothermal well, may exceed 200° C.
Such an overheating frequently results in failure or reduced useful life for thermally exposed electronic components. Thus, there is a need to reduce the temperature within the downhole tool in the sections containing the electronic components to within the safe operational level of the components.
Accordingly, it is desirable to have a downhole drilling system that can be maintained or controlled in a manner to reduce the effects of the overheating.